Th350 exploded view8/25/2023 ![]() This is an electronically controlled transmission that is still being produced and used in a range of heavy-duty GM and military cars/trucks. Around the same time when the TH400’s name was changed, an overdrive version called the 4L80-E was launched. The change in naming does not come as surprise since some GM transmissions were also renamed (for example the 700R4 to 4L60). GVW or Gross Vehicle Weight) in 1990 to make it easier for buyers to identify the transmission. ![]() The naming of the TH400 was changed to 3L80 (3-speeds, Longitudinally positioned, 8000 lbs. In the 1970s, the TH400 was used in heavier-duty GM trucks and it was available in 2wd and 4wd configurations. This stator helped to vary the torque converter’s characteristics, and you can tell a car has this stator by the two-prong plug on the case. Buick, Olds, and Cadillacs that were later launched between 1965-1967 also featured the transmission but with an innovative variable-pitch stator. Upon its launch, the TH400 was evident in Buicks and Cadillacs, and a year later, it was used in Chevrolet and Oldsmobile cars. It was used in a wide range of vehicles, hence, it was not just exclusive to GM cars. The TH400 was launched by General Motors in 1964, as a replacement to the ST300 2-speed automatic transmission. of input torque, nonetheless, aftermarket designs that have been modified may go beyond that rating. This placement is aimed at providing the best power ratio and durability for rear-wheel drive. The GM TH400 transmission is a three-speed automatic transmission that was longitudinally positioned behind the engine. The TH400’s high-level of adoption could be tied to its remarkable features, and it proved that people can once again rely on GM transmissions.īut what were these features sported by this durable and legendary transmission, and generally, what set it apart from other transmissions from this manufacturer? An overview of the TH400 transmission will give you a better idea. This popular transmission was found in GM’s cars, as well as, Rolls-Royces, Jeeps, Jaguars, Ferraris, etc. So, if you find yourself in this predicament, find a safe place to pull off the road and shut the engine off, wait a minute or so and then restart it.The TH400 or Turbo 400 is a good transmission that was used in several cars years ago. So, avoid extended driving when the transmission is in fail safe mode.Ī transmission that goes into limp mode will sometimes reset itself when the engine is shut off and restarted. Excessive heat build up in an automatic transmission is the #1 cause of catastrophic failure. Maximum speed while in limp mode is around 30 mph.Ĭontinuing to drive the vehicle with the transmission in fail safe or driving faster than the recommended fail safe speed will cause the transmission to overheat. When the transmission is in fail safe mode, the vehicle should only be drive home or to the repair shop. In fail safe/limp mode, the transmission will have limited functionality and will lock in either 2nd. This can be described as shifting into the wrong gear, skipping the intended gear and shifting back and forth between two gears.Ī failed transmission solenoid or an open circuit anywhere in the electrical system may cause the transmission to go into Fail Safe (or “limp” mode as it is also called) in order to protect the transmission from internal damage that might be caused by the faulty solenoid or open circuit. A faulty shift solenoid can cause the transmission to downshift uncontrollably (in other words at random times) or not downshift at all, even when coming to a complete stop.Įrratic Shifts: A defective shift solenoid can also cause the transmission to shift erratically. When the vehicle comes to a complete stop the transmission downshifts into first gear. No Downshift(s): When the shift solenoids are function properly, the transmission automatically downshifts as the vehicle speed slows. These shift delays can occur when you first shift the transmission into a gear and when the transmission is shifting between gears. During a shift delay no power is delivered to the drive wheels – it’s as if the shifter is in neutral. A faulty shift solenoid can cause delayed shifts of a few seconds or up to one minute or longer. There primary problem symptoms of a faulty shift solenoid are delayed shifts, no downshifts and erratic shifts.ĭelayed Shifts: When the shift solenoids are working properly, shifts occur smoothly and without delay.
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